A bifunctional protein consisting of aspartokinase, and homoserine dehydrogenase activities. It is found primarily in BACTERIA and in PLANTS.
An enzyme that catalyzes the reduction of aspartic beta-semialdehyde to homoserine, which is the branch point in biosynthesis of methionine, lysine, threonine and leucine from aspartic acid. EC
An enzyme that catalyzes the formation of beta-aspartyl phosphate from aspartic acid and ATP. Threonine serves as an allosteric regulator of this enzyme to control the biosynthetic pathway from aspartic acid to threonine. EC
An enzyme that catalyzes the conversion of L-aspartate 4-semialdehyde, orthophosphate, and NADP+ to yield L-4-aspartyl phosphate and NADPH. EC
An essential amino acid occurring naturally in the L-form, which is the active form. It is found in eggs, milk, gelatin, and other proteins.
A subclass of enzymes which includes all dehydrogenases acting on primary and secondary alcohols as well as hemiacetals. They are further classified according to the acceptor which can be NAD+ or NADP+ (subclass 1.1.1), cytochrome (1.1.2), oxygen (1.1.3), quinone (1.1.5), or another acceptor (1.1.99).
A rather large group of enzymes comprising not only those transferring phosphate but also diphosphate, nucleotidyl residues, and others. These have also been subdivided according to the acceptor group. (From Enzyme Nomenclature, 1992) EC 2.7.
A species of gram-negative, facultatively anaerobic, rod-shaped bacteria found in soil, water, food, and clinical specimens. It is a prominent opportunistic pathogen for hospitalized patients.
One of the FURANS with a carbonyl thereby forming a cyclic lactone. It is an endogenous compound made from gamma-aminobutyrate and is the precursor of gamma-hydroxybutyrate. It is also used as a pharmacological agent and solvent.
Systems of enzymes which function sequentially by catalyzing consecutive reactions linked by common metabolic intermediates. They may involve simply a transfer of water molecules or hydrogen atoms and may be associated with large supramolecular structures such as MITOCHONDRIA or RIBOSOMES.
A genus of asporogenous bacteria that is widely distributed in nature. Its organisms appear as straight to slightly curved rods and are known to be human and animal parasites and pathogens.
One of the non-essential amino acids commonly occurring in the L-form. It is found in animals and plants, especially in sugar cane and sugar beets. It may be a neurotransmitter.
A species of gram-negative, facultatively anaerobic, rod-shaped bacteria (GRAM-NEGATIVE FACULTATIVELY ANAEROBIC RODS) commonly found in the lower part of the intestine of warm-blooded animals. It is usually nonpathogenic, but some strains are known to produce DIARRHEA and pyogenic infections. Pathogenic strains (virotypes) are classified by their specific pathogenic mechanisms such as toxins (ENTEROTOXIGENIC ESCHERICHIA COLI), etc.
The first enzyme in the METHIONINE biosynthetic pathway, this enzyme catalyzes the succinylation reaction of L-homoserine to O-succinyl-L-homoserine and COENZYME A using succinyl-CoA.
Cyclic esters of acylated BUTYRIC ACID containing four carbons in the ring.
A tetrameric enzyme that, along with the coenzyme NAD+, catalyzes the interconversion of LACTATE and PYRUVATE. In vertebrates, genes for three different subunits (LDH-A, LDH-B and LDH-C) exist.
The rate dynamics in chemical or physical systems.
The functional hereditary units of BACTERIA.
A zinc-containing enzyme which oxidizes primary and secondary alcohols or hemiacetals in the presence of NAD. In alcoholic fermentation, it catalyzes the final step of reducing an aldehyde to an alcohol in the presence of NADH and hydrogen.
Descriptions of specific amino acid, carbohydrate, or nucleotide sequences which have appeared in the published literature and/or are deposited in and maintained by databanks such as GENBANK, European Molecular Biology Laboratory (EMBL), National Biomedical Research Foundation (NBRF), or other sequence repositories.
The order of amino acids as they occur in a polypeptide chain. This is referred to as the primary structure of proteins. It is of fundamental importance in determining PROTEIN CONFORMATION.
Organic compounds that generally contain an amino (-NH2) and a carboxyl (-COOH) group. Twenty alpha-amino acids are the subunits which are polymerized to form proteins.
A family of compounds containing an oxo group with the general structure of 1,5-pentanedioic acid. (From Lehninger, Principles of Biochemistry, 1982, p442)
Works containing information articles on subjects in every field of knowledge, usually arranged in alphabetical order, or a similar work limited to a special field or subject. (From The ALA Glossary of Library and Information Science, 1983)
A series of oxidative reactions in the breakdown of acetyl units derived from GLUCOSE; FATTY ACIDS; or AMINO ACIDS by means of tricarboxylic acid intermediates. The end products are CARBON DIOXIDE, water, and energy in the form of phosphate bonds.
Enzyme that catalyzes the first step of the tricarboxylic acid cycle (CITRIC ACID CYCLE). It catalyzes the reaction of oxaloacetate and acetyl CoA to form citrate and coenzyme A. This enzyme was formerly listed as EC
An enzyme that catalyzes the conversion of L-glutamate and water to 2-oxoglutarate and NH3 in the presence of NAD+. (From Enzyme Nomenclature, 1992) EC
A genus of VIBRIONACEAE, made up of short, slightly curved, motile, gram-negative rods. Various species produce cholera and other gastrointestinal disorders as well as abortion in sheep and cattle.
The order Actiniaria, in the class ANTHOZOA, comprised of large, solitary polyps. All species are carnivorous.
The pattern of GENE EXPRESSION at the level of genetic transcription in a specific organism or under specific circumstances in specific cells.
The relationship between two different species of organisms that are interdependent; each gains benefits from the other or a relationship between different species where both of the organisms in question benefit from the presence of the other.
Flagellate EUKARYOTES, found mainly in the oceans. They are characterized by the presence of transverse and longitudinal flagella which propel the organisms in a rotating manner through the water. Dinoflagellida were formerly members of the class Phytomastigophorea under the old five kingdom paradigm.
A phylum of radially symmetrical invertebrates characterized by possession of stinging cells called nematocysts. It includes the classes ANTHOZOA; CUBOZOA; HYDROZOA, and SCYPHOZOA. Members carry CNIDARIAN VENOMS.
The determination of the pattern of genes expressed at the level of GENETIC TRANSCRIPTION, under specific circumstances or in a specific cell.
Processes occurring in various organisms by which new genes are copied. Gene duplication may result in a MULTIGENE FAMILY; supergenes or PSEUDOGENES.
Amino acid transporter systems capable of transporting acidic amino acids (AMINO ACIDS, ACIDIC).
The state of weariness following a period of exertion, mental or physical, characterized by a decreased capacity for work and reduced efficiency to respond to stimuli.
A group of diseases related to a deficiency of the enzyme ARGININOSUCCINATE SYNTHASE which causes an elevation of serum levels of CITRULLINE. In neonates, clinical manifestations include lethargy, hypotonia, and SEIZURES. Milder forms also occur. Childhood and adult forms may present with recurrent episodes of intermittent weakness, lethargy, ATAXIA, behavioral changes, and DYSARTHRIA. (From Menkes, Textbook of Child Neurology, 5th ed, p49)
Membrane transporters that co-transport two or more dissimilar molecules in the opposite direction across a membrane. Usually the transport of one ion or molecule is against its electrochemical gradient and is "powered" by the movement of another ion or molecule with its electrochemical gradient.
Databases containing information about PROTEINS such as AMINO ACID SEQUENCE; PROTEIN CONFORMATION; and other properties.
Proteins involved in the transport of specific substances across the membranes of the MITOCHONDRIA.
A mechanism of communication with a physiological system for homeostasis, adaptation, etc. Physiological feedback is mediated through extensive feedback mechanisms that use physiological cues as feedback loop signals to control other systems.
The modification of the reactivity of ENZYMES by the binding of effectors to sites (ALLOSTERIC SITES) on the enzymes other than the substrate BINDING SITES.

Mechanism of control of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase by threonine. (1/18)

The regulatory domain of the bifunctional threonine-sensitive aspartate kinase homoserine dehydrogenase contains two homologous subdomains defined by a common loop-alpha helix-loop-beta strand-loop-beta strand motif. This motif is homologous with that found in the two subdomains of the biosynthetic threonine-deaminase regulatory domain. Comparisons of the primary and secondary structures of the two enzymes allowed us to predict the location and identity of the amino acid residues potentially involved in two threonine-binding sites of Arabidopsis thaliana aspartate kinase-homoserine dehydrogenase. These amino acids were then mutated and activity measurements were carried out to test this hypothesis. Steady-state kinetic experiments on the wild-type and mutant enzymes demonstrated that each regulatory domain of the monomers of aspartate kinase-homoserine dehydrogenase possesses two nonequivalent threonine-binding sites constituted in part by Gln(443) and Gln(524). Our results also demonstrated that threonine interaction with Gln(443) leads to inhibition of aspartate kinase activity and facilitates the binding of a second threonine on Gln(524). Interaction of this second threonine with Gln(524) leads to inhibition of homoserine dehydrogenase activity.  (+info)

Isolation of the aspartokinase domain of bifunctional aspartokinase I-homoserine dehydrogenase I from E.coli K12. (2/18)

A proteolytic fragment (Mr approximately 25 000) carrying only the aspartokinase activity has been purified by chromatofocusing after limited proteolysis of aspartokinase I-homoserine dehydrogenase I from E.coli K12. The NH2-terminal sequence shows that it corresponds to the amino terminal peptide of the native enzyme. The results confirm a previous hypothesis about the organization of native aspartokinase I-homoserine dehydrogenase I.  (+info)

Cloning and nucleotide sequence of the Bacillus subtilis hom gene coding for homoserine dehydrogenase. Structural and evolutionary relationships with Escherichia coli aspartokinases-homoserine dehydrogenases I and II. (3/18)

The Bacillus subtilis hom gene, encoding homoserine dehydrogenase (L-homoserine:NADP+ oxidoreductase, EC has been cloned and its nucleotide sequence determined. The B. subtilis enzyme expressed in Escherichia coli is sensitive by inhibition by threonine and allows complementation of a strain lacking homoserine dehydrogenases I and II. Nucleotide sequence analysis indicates that the hom stop codon overlaps the start codon of thrC (threonine synthase) suggesting that these genes, as well as thrB (homoserine kinase) located downstream from thrC, belong to the same transcription unit. The deduced amino acid sequence of the B. subtilis homoserine dehydrogenase shows extensive similarity with the C-terminal part of E. coli aspartokinases-homoserine dehydrogenases I and II; this similarity starts at the exact point where the similarity between E. coli or B. subtilis aspartokinases and E. coli aspartokinases-homoserine dehydrogenases stops. These data suggest that the E. coli bifunctional polypeptide could have resulted from the direct fusion of ancestral aspartokinase and homoserine dehydrogenase. The B. subtilis homoserine dehydrogenase has a C-terminal extension of about 100 residues (relative to the E. coli enzymes) that could be involved in the regulation of the enzyme activity.  (+info)

Subunit structure of the methionine-repressible aspartokinase II--homoserine dehydrogenase II from Escherichia coli K12. (4/18)

The quaternary structure of Escherichia coli K12 aspartokinase II--homoserine dehydrogenase II has been examined. This multifunctional protein has a molecular weight Mr = 176000. It is composed of two subunits having the same molecular weight and the same charge. The results obtained from the examination of tryptic maps, the number and amino acid composition of cysteine-containing peptides and the uniqueness of the N-terminal sequence, strongly suggest that the 2 subunits are identical. The properties of aspartokinase II--homoserine dehydrogenase II can be compared to those of the much better known protein aspartokinase I--homoserine dehydrogenase I.  (+info)

Threonine-sensitive homoserine dehydrogenase and aspartokinase activities of Escherichia coli K12. Kinetic and spectroscopic effects upon binding of serine and threonine. (5/18)

The two threonine-sensitive activities aspartokinase and homoserine dehydrogenase are inhibited by L-serine. The inhibition of the aspartokinase by L-serine displays homotropic cooperative effects and is competitive versus aspartate. The inhibition by L-serine of the homoserine dehydrogenase displays Michaelis-Menten kinetics which are of a competitive nature versus homoserine. Characteristic effects of L-serine on the protein include a perturbation of its absorption and fluorescence spectra, with an increase in the fluorescence of the protein-NADPH complex. L-serine shifts the allosteric equilibrium of the protein to a "T-like" conformation to which L-threonine binds noncooperatively. L-Serine, a threonine analog, is not capable, as the physiological effector, of inducing a complete R to T transition of the enzyme; the aspartokinase globules show a cooperative conformation change upon serine binding, but this conformation change is not found in the homoserine dehydrogenase globules.  (+info)

Proteolysis of the bifunctional methionine-repressible aspartokinase II-homoserine dehydrogenase II of Escherichia coli K12. Production of an active homoserine dehydrogenase fragment. (6/18)

The dimeric bifunctional enzyme aspartokinase II-homoserine dehydrogenase II (Mr = 2 X 88,000) of Escherichia coli K12 can be cleaved into two nonoverlapping fragments by limited proteolysis with subtilisin. These two fragments can be separated under nondenaturing conditions as dimeric species, which indicates that each fragment has retained some of the association areas involved in the conformation of the native protein. The smaller fragment (Mr = 2 X 24,000) is devoid of aspartokinase and homoserine dehydrogenase activity. The larger fragment (Mr = 2 X 37,000) is endowed with full homoserine dehydrogenase activity. These results show that the polypeptide chains of the native enzyme are organized in two different domains, that both domains participate in building up the native dimeric structure, and that one of these domains only is responsible for homoserine dehydrogenase activity. A model of aspartokinase II-homoserine dehydrogenase II is proposed, which accounts for the present results.  (+info)

The threonine-sensitive homoserine dehydrogenase and aspartokinase activities of Escherichia coli K12. Carboxymethylation of the enzyme: threonine binding and inhibition are functionally dissociable. (7/18)

The inactivation of the aspartokinase I-homoserine dehydrogenase I by iodoacetic acid and the effect on the sensitivity to its inhibitor, L-threonine, were examined. Both aspartokinase and homoserine dehydrogenase inactivation, as well as the dehydrogenase desensitization toward L-threonine occur as a pseudo-first order process. During its inactivation, the aspartokinase remains sensitive to L-threonine. At 50% inactivation, the inhibition curve of the aspartokinase by L-threonine displays homotropic cooperative effects. This alkylated protein retains eight binding sites for L-threonine. During the carboxymethylation, the protein remains in the tetrameric form until half of the kinase activity is lost. At the end of the inactivation aggregate forms and dimers appear.  (+info)

The primary structure of Escherichia coli K12 aspartokinase I-homoserine dehydrogenase I. Site of limited proteolytic cleavage by subtilisin. (8/18)

The sequence of the first 25 residues of the homoserine dehydrogenase fragment, produced by limited proteolysis of aspartokinase I-homoserine dehydrogenase I with substilisin, has been determined. The sequence of a cyanogen bromide peptide (CB5, 59 residues), isolated from the entire protein, is also presented. Residues 1 to 18 of the subtilisin homoserine dehydrogenase fragment match the sequence 42 to 59 of peptide CB5.  (+info)

cd04881 (PSSM ID: 153153): Conserved Protein Domain Family ACT_HSDH-Hom, The ACT_HSDH_Hom CD includes the C-terminal ACT domain of the NAD(P)H-dependent, homoserine dehydrogenase (HSDH) encoded by the hom gene of Bacillus subtilis and other related sequences
K00928 lysC; aspartate kinase [EC:] K00928 lysC; aspartate kinase [EC:] K00928 lysC; aspartate kinase [EC:] K12524 thrA; bifunctional aspartokinase / homoserine dehydrogenase 1 [EC:] K12525 metL; bifunctional aspartokinase / homoserine dehydrogenase 2 [EC: ...
Introduction: Aspartokinase (A1, A2, A3) Homoserine dehydrogenase (B1, B2) Threonine dehydratase (C1, C2) Allosteric regulation of selective isozymes some unregulated Sequential feedback inhibition Same product inhibits its biosynthetic path at multiple sites Inhibits first enzyme in pathway
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Dr Allan Goldman trained as a doctor in South Africa before coming to London in 1990. He completed his paediatric intensive care specialisation in both London and Australia. He took up the post of consultant at Great Ormond Street Hospital (GOSH) in 1998. ...
Numerous hits in gapped BLAST to NADH dehydrogenase I chain A / NADH-ubiquinone oxidoreductase sequences,e.g.residues 1-118 are 55% similar to NADH-ubiquinone dehydrogenase chain A 1 from Mesorhizobium loti (14022149,).Residues 6-117 are 32% similar to NADH dehydrogenase I chain A from Escherichia coli O157:H7 (13362642,). Residues 6-117 are 34% similar o NADH dehydrogenase I chain A from Pseudomonas aeruginosa strain PAO1 (gb,AAG06025.1 ...
This HMM represents a subfamily of small, transmembrane proteins believed to be components of Na+/H+ and K+/H+ antiporters. Members, including proteins designated MnhG from Staphylococcus aureus and PhaG from Rhizobium meliloti, show some similarity to chain L of the NADH dehydrogenase I, which also translocates protons ...
H+/e- stoichiometry for NADH dehydrogenase I and dimethyl sulfoxide reductase in anaerobically grown Escherichia coli cells.: Anaerobically grown Escherichia co
Numerous significant hits using gapped BLAST to aspartokinase III from E. coli (416597), Arabidopsis thaliana (6091740, putative), Methanococcus jannaschii (2492982), among others. HD1375 is 57% similar to residues 1-449 from AK3_ECOLI ...
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In molecular biology, the amino acid kinase domain is a protein domain. It is found in protein kinases with various specificities, including the aspartate, glutamate and uridylate kinase families. In prokaryotes and plants the synthesis of the essential amino acids lysine and threonine is predominantly regulated by feed-back inhibition of aspartate kinase (AK) and dihydrodipicolinate synthase (DHPS). In Escherichia coli, thrA, metLM, and lysC encode aspartokinase isozymes that show feedback inhibition by threonine, methionine, and lysine, respectively. The lysine-sensitive isoenzyme of aspartate kinase from spinach leaves has a subunit composition of 4 large and 4 small subunits. In plants although the control of carbon fixation and nitrogen assimilation has been studied in detail, relatively little is known about the regulation of carbon and nitrogen flow into amino acids. The metabolic regulation of expression of an Arabidopsis thaliana aspartate kinase/homoserine dehydrogenase (AK/HSD) gene, ...
• The permeability of the blood-retina barrier was tested in rats with early streptozocin-induced diabetes. Two different tracer substances were used: fluoresce

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